Alloy and method of making same



Patented July 31, 1934 v UNITED STATES ALLOY. AND METHOD OF MAKING SAME Clarence W. Balke, Highland Park, Ill., assignor, by mesne assignments, to" Rametflorporation of America, North Chicago, 111., a corporation of Illinois No Drawing. Application May. 29; 1930, Serial No. 457,496

13 Claims.

This invention relates in general to alloys and a method of producing the same, and while it has generally for an object the provision and production of an extremely hard and strong alloy having very great wear resisting qualities, the

invention has more particular reference to the provision and production of alloys composed of a refractory metal and a metalloid, which will adapt such alloys for use in the formation of tools for cutting and working other metals. The invention contemplates the provision of a very hard alloy comprising a refractory metal,

such as tantalum, columbium or tungsten chem-' ically unitedwith' a metalloid, such as boron. This boride is heat treated with another metal to provide an alloy suitable for the formation of getal cutting or working tools, or aswire drawing es. Alloys for the formation of metal cutting and working tools have heretofore consisted of various combinations of metals with the refractory metals and carbon. While such alloys possessa high degree of hardness and wear resisting qualities, it has been found that a refractory metal 5 boride combined with an auxiliary metal is considerably harder and possesses the desirable qual-' ities which are requisite in metal working or cutting tools and wire dies.

It is a primary object of this invention to pro- 0 vide a tantalum boride alloy and a method of producing such an alloy.

An important object of the invention is the provision and production of a hard metal alloy which includes boron and a refractory metal.

Another important object of the invention is the production of a novel alloy, comprising a refractory metal, the boride of the refractory metal, and another metal.

Other objects and advantages of the invention 40 will be apparent from the following description which discloses a preferred embodiment of the invention.

The novel method for producing the extremely hard alloy of the present invention briefly com- 5 prises uniting a refractory metal powder, such as tantalum, columbium, molybdenum, or tungsten powder with boron, whiclrhas been preheated to purify it. It will be understood that amorphous boron and various chemical compositions which will give boron when heated, such as the composition having the chemical formula of BC, are

here contemplated as coming within the scope of the presentinvention. The refractory metal powder and the boron are then heated in an evacuated. electric furnace and are ground to a very finely divided powder. This finely divided powder is next mixed with a hydrogen reduced metallic powder of one or more metals of the on group, and the boride and metallic powders are very thoroughly mixed and ground to an extremely finely divided powder.

After thoroughly mixing the boride powder with that of themetal or metals of the iron group and grinding them to a very finely divided form, the mixture is then subjected-to tremendous pressure to form a substantially non-porous and homogeneous body of the desired size and shape. This non-porous and homogeneous body is subjected to a heat'treatment in a vacuum at from 1350" to 1400 C.

This heat treatment'serves to combine the degasified constituents in the form of a solid homogeneous alloy having an exceedingly fine grain and providing a very hard composition suitable for use in the manufacture of metal cutting or working tools and wire dies, and for other uses requiring an alloy having wear resisting qualities combined with extreme hardness and great strength.

Attention is here directed, before proceeding with the disclosure of the invention, to the tremendous pressure referred to above in forming the mixed and ground powders into a homogeneous body having a relatively fine grain. This pressure is suflicient to permit handling and readily-forming the body to a desired shape and size prior to the heat treatment, which combines or unites the constituents of the alloy, and in practice, a pressure of about eighty tons per square inch is used.

In carrying out the invention to accomplish the above mentioned objects, it is desirable to provide a suflicient quantity of the refractory metal that some of it may combine with the metalloid and the remainder with another metal forming tne alloy.

The boron employed to produce the boride is preferably in the form of amorphous boron which has been preheated to about 1500 C. to volatilize any organic matter contained in the boron and to rid it of objectionable gases. After such purification, the boron is mixed with a refractory metal powder, such as tantalum powder in about the proportion of from 3 to 6% boron and 97 to 94% tantalum by weight. This mixture is ground and mixed in a ball mill and then placed in a cylinder or crucible of tantalum sheet with a tight fitting tantalum cover.

The loaded tantalum cylinder is placed in a graphite crucible and completely surrounded with tantalum powder in drder to prevent oxygen or nitrogen from the air from passing into the tantalum boron mixture. The carbon crucible is then placed in graphite and heated in a high frequency furnace by slowly raising the temperature to about 2000 C. and maintaining this temperature for about one-half hour to chemically unite the boron and tantalum. When this crucible of carbon has been heated sufficiently to become red hot, a very violent and explosive reaction takes place, so that possibly a part'of the boron powder may be blown out of the reacting mixture.

The tantalum boron composition that results from the foregoing uniting operation is a tantalum boride having from 3 to 6% by weight of boron, and after cooling is brownish-grey in color. This powder is exceedingly hard and readily scratches the various hard metal alloys now used for the formation of cutting tools. This tantalum boride is next ground in a ball mill for about twenty-four hours to a finely divided powder and heated to. from 1600 to 1700 in a vacuum furnace to degasify and to complete the reaction between the refractory metal and the boron. The boride powder may be subjected to suflicient pressure to hold the particles together under the ac on of the vacuum pump before subjecting it to the foregoing heat treatment. -This latter heat treatment also serves to reduce air spaces among the particles. of the powder.

The boride is then ready for mixing with an auxiliary metal to form a homogeneous alloy. While this auxiliary metal may be any suitable base metal having a fusing or sintering tempera ture below the melting point of the boride, and which will alloy with the refractory metal used at a comparatively low temperature, the present embodiment of the invention contemplates the provision of one or more metals of the iron group, such as, iron, nickel and cobalt. Preferably from 3 to by weight of a hydrogen reduced nickel powder in finely divided form is used in the alloy, although a mixture of nickel powder and iron powder, comprising from 3 to 15% by weight of the composition has been found to produce a very hard alloy which gives excellent results when formed as a tool.

As already mentioned, from 3 to 15% by weight of hydrogen'reduced nickel powder is mixed with the boride powder; for example, tantalum boride, and this mixture is ground for about ninety hours in a ball mill to an extremely fine powder, the particles of which are thoroughly and uniformly mixed tantalum boride and nickel.

This mixture is next subjected to a tremendous pressure to the order of about eighty tons per square inch, sufficient to press the powder mixture into a body, which maybe handled and formed, or worked to the desired shape and size.

When this powder mixture has been so formed, it

is heated in a vacuum at from 1350 to 1400 C. and this temperature maintained for about one hour. The resulting alloy has a very fine grain due to the degasifying of the,boride, the thorough mixing of the fine powders, the tremendous pressure used to press the mixture for forming prior to the last heat treatment and to the final heat treatment in the vacuum.

One of the alloys made by the foregoing method comprises the following percentages by weight of the materials indicated:

Percent Nickel 3-15 Tantalum boride 97-85 Another alloy contemplated as within the scope of the invention is:

Knowledge of the theory of producing a refrac tory metal boride having an excess of the refractory metal is not necessary to a complete understanding of this invention, and it will be understood that the invention is not limited by the recitation of a possible explanation of this hard and wear-resistant alloy. It is believed that some of the tantalum of the boride is chemically free and combines with the nickel or auxiliary metal to provide an extremely hard bond or cementing material for the tantalum boride, and that this free or uncombined portion of the refractory metal may be considered as being the excess of that required to form the boride of the refractory metal.

Thus, a .novel alloy is produced which is sufficiently'hard to be used in the formation of metal cutting and working tools, and wire drawing dies. Tools made of this alloy will scratch the tools in use at present, and yet are sufliciently strong and durable or wear resisting as not to crumble,

break or chip readily when used as a tool, such,

as a 'wire drawing die, to cut or work other hard metals.

Having thus described my invention, what'I claim is new and desire to secure by Letters Patent of the United States, is:

1. A hard alloy composed of a tantalum boride, and from 3 to 15% of an auxiliary metal of the iron group.

2. An alloy consisting of tantalum boride and substantially 8% of nickel.

3. An alloy comprising from 3 to 15% nickel and the remainder tantalum and boron in proportion of from 3 to 6% boron and 97 to 94% tantalum.

4. A method of producing a hard alloy of tantalum which comprises heat treating a mixture of tantalum and boron in a vacuum, mixing a powdered auxiliary metal of the iron group with the boride thus formed, and heating the auxiliary metal and the tantalum boride in a vacuum.

5. A method of producing a hard tantalum alloy which comprises chemically uniting tantalum powder with boron, heat treating the tantalum boron composition in a vacuum, pressing a powder of a metal of the iron group with said tantalum boron composition, and heating the mixture in a vacuum.

6. A hard .and tough alloy consisting of from to 97% of degasified tantalum boride' and from 15% to 3% by weight of nickel.

7. A hard and tough composition composed of tantalum boride alloy including tantalum boride having a boron content ranging between 3% and 6% by weight of said boride, and a metal of the iron group making up from 3% to 15% by weight of the alloy.

8. A hard composition composed of an alloy of a hard refractory metal boride including a boride of a hard refractory metal from the group composedof tantalum and columbium, and an auxiliary metal of the iron group making up from 3% to 15% by weight of the alloy, said boride of said hard refractory metal having a boron content ranging from 3% to 6% by weight of the boride.

9. A hard alloy consisting of a boride of a hard refractory metal from the group composed of tantalum and co1umbium, said'boride making up from 85% to 97% by weight of the alloy, and one or more-metals of the iron group making up from 15%. to 3% by weight of the alloy.

10. A method of producing a hard alloy of a metal from the group composed of tantalum and columbium, which comprises heat-treating a mixture of'said metal and boron in a vacuum, mixing a powdered auxiliary metal of the iron group with the boride thus formed, and heating the auxiliary; metal and the boride in a vacuum.

- 11. A method of producing'a hard alloy of a metal from the group composed of tantalum and columbium, which comprises heat-treating a powder mixture of boron and said metal from said group composed of tantalum and columbium, whereby a boride thereof is formed, mixing a powder of one or more metals of the iron group with said boride, pressing the mixture, and combining the pressed mixture by heating it in a vacuum.

12. A method of producing a hard alloy of one or more metals of the iron ,group with a boride of a metal from the group composedof tantalum and columbium, said boride having a boron content of from 3% to 6% byweight of the boride. which comprises heat-treating the said boride in a finely divided state to degasify said boride, mixing therewith said one or more metals or said iron group in a finely divided state, and heating the mixture in a vacuum.

13. A method of producing an alloy of a metal from the group composed of tantalum and colum- 

